The introduction of drug-eluting stents (DES) has been a major advancement in the field of cardiovascular medicine due to the ability of the stents, which are coated with a drug, to prevent restenosis of a vessel. Previous bare metal stents were only able to reduce the rate of restenosis, caused by intimal hyperplasia, to approximately 20-25%. The medicine or drug that is associated with the DES is delivered directly to the blockage site, reducing restenosis rates even further. However, implantable medical devices that are pre-coated with drugs may have a significantly shorter shelf-life than their non-coated counterparts. For example, the potency of the drug may decrease over time, such that the expiration date of the device must take into account the degradation of drug. In addition, viability concerns may prevent one from manufacturing a stent pre-coated with drugs and substances that degenerate within a short period of time at room temperature. For example, drugs, which are based on large molecule biologics (e.g., DNA, protein, monoclonal antibodies, etc.) may be particularly susceptible to degradation, and therefore are difficult to implement as a pre-coated layer on a stent. Furthermore, because most pre-coated devices do not permit the medical practitioner to change or modify the drug associated with the device, the pre-coated devices may limit the medical practitioner's ability to determine and implement the best medication/device combination based on specific treatment needs.
Examples of current drug delivery devices and methods are disclosed in U.S. Patent Application, Publication No. 2004/0010309 A1, titled “METHODS AND SYSTEMS FOR DELIVERING LIQUID SUBSTANCES TO TISSUES SURROUNDING BODY LUMENS” by Seward et al., published Jan. 15, 2004; U.S. Pat. No. 6,699,282 B1 titled “METHOD AND APPARATUS FOR DELIVERY OF MEDICATION” issued to Sceusa, dated Mar. 2, 2004; U.S. Pat. No. 6,656,162 B2 titled “IMPLANTABLE DRUG DELIVERY STENTS” issued to Santini, Jr. et al., dated Dec. 2, 2003; U.S. Pat. No. 6,613,084 B2 titled “STENT HAVING COVER WITH DRUG DELIVERY CAPABILITY” issued to Yang, dated Sep. 2, 2003; U.S. Pat. No. 6,344,028 B1 titled “REPLENISHABLE STENT AND DELIVERY SYSTEM” issued to Barry, dated Feb. 5, 2002; U.S. Pat. No. 5,954,693 titled “REPLENISHABLE STENT AND DELIVERY SYSTEM” issued to Barry, dated Sep. 21, 1999; U.S. Pat. No. 5,857,998 titled “STENT AND THERAPEUTIC DELIVERY SYSTEM” issued to Barry, dated Jan. 12, 1999; U.S. Pat. No. 5,755,722 titled “STENT PLACEMENT DEVICE WITH MEDICATION DISPENSER AND METHOD” issued to Barry et al., dated May 26, 1998; U.S. Pat. No. 5,685,847 titled “STENT AND THERAPEUTIC SYSTEM” issued to Barry, dated Nov. 11, 1997; and U.S. Pat. No. 5,439,446 titled “STENT AND THERAPEUTIC SYSTEM” issued to Barry, dated Aug. 8, 1995; each of which is incorporated herein by reference in its entirety.